Single-fiber one-way based multi-time-frequency signal simultaneous transmission method, transmitting end and receiving end

Abstract

The application discloses a kind of based on single-fiber unidirectional multiple time-frequency signal simultaneous transmission method, sending end and receiving end, specifically related to digital communication technical field;The sending end of the present application receives multiple time-frequency signals for fusion processing, and uses time division multiplexing to transmit multiple time-frequency signals based on single-fiber unidirectional single-wavelength mode, and the receiving end recovers the original time-frequency signal fusion processing from the mixed time-frequency signal to complete multiple time-frequency signal output, so as to improve the utilization of transmission medium, reduce cost and facilitate engineering deployment;In addition, a time source fusion algorithm is also innovatively proposed, which dynamically adjusts the weight of the phase difference of each time source in the fusion phase difference based on the variance of the phase difference of the local core time of different time sources, and then dynamically calculates the time source fusion phase difference to improve the system timing accuracy under multiple time sources;Compared with single-fiber unidirectional wavelength division multiplexing mode, the present application has the advantages of consistent multiple time-frequency signal transmission delay, simple hardware design and low cost.

Description

Technical Field

[0001] This invention relates to the field of digital communication technology, and in particular to a method for simultaneous transmission of multiple time-frequency signals based on a single fiber and unidirectional transmission, as well as a transmitter and a receiver. Background Technology

[0002] Currently, the mainstream technologies for long-distance precision time and frequency transmission include fiber optic time and frequency transmission, satellite time and frequency transmission, and laser time and frequency transmission. Fiber optic time and frequency transmission technology offers advantages such as large transmission bandwidth, stable transmission, long transmission distance, strong anti-interference capability, low loss, simple structure, and high timing accuracy. Furthermore, its good compatibility with fiber optic communication systems has led to its widespread application in long-distance precision time and frequency transmission. With the further popularization of fiber optics, fiber optic time and frequency transmission technology has become a highly promising technology for long-distance precision time and frequency transmission.

[0003] Currently, to improve the timing accuracy of time and frequency signals and reduce the impact of bidirectional transmission asymmetry in fiber optic links on timing accuracy, single-fiber bidirectional transmission is generally adopted for long-distance transmission of precise time and frequency signals. However, in telecommunications operator networks, when transmitting long-distance fiber optic links, unidirectional erbium-doped fiber amplifiers (EDFAs) are typically used to amplify the optical signal, making single-fiber bidirectional timing incompatible with telecommunications operator fiber optic communication networks. In some special applications with high security requirements, unidirectional timing is preferred to control the risk of data leakage. Furthermore, some applications require the simultaneous long-distance transmission of multiple time and frequency signals over a single fiber, with multiple time and frequency signals output at the receiving end.

[0004] Therefore, there is an urgent need for a new method for simultaneous transmission of multiple time-frequency signals based on single-fiber unidirectional transmission, which can be compatible with existing unidirectional optical amplification networks, meet the requirements of high-security unidirectional transmission, and achieve high-precision, high-delay consistency simultaneous transmission of multiple time-frequency signals with low cost and low complexity. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method and system for simultaneous transmission of multiple time and frequency signals based on single-fiber unidirectional transmission. It aims to achieve advantages such as consistent transmission delay of multiple time and frequency signals, simple hardware design and low cost, improve the system timing accuracy under multiple time source conditions, and ensure the robustness of the system's stable output when the time and frequency sources are abnormal.

[0006] To achieve the above objectives, this application proposes a method for simultaneous transmission of multiple time-frequency signals based on a single-fiber unidirectional transmission, including a transmitting end processing step and a receiving end processing step; wherein,

[0007] The various time-frequency signals include time source signals and frequency source signals; the time source signals include 1PPS+TOD signals and DCLS signals, and the frequency source signals include 1PPS+TOD signals, DCLS signals, and E1 signals;

[0008] The sending end processing steps include:

[0009] It receives time source signals and frequency source signals, decodes the time source signals to obtain time source information and phase, and decodes and extracts the frequency source signals to obtain frequency information.

[0010] Based on the time source information and phase obtained from decoding, maintain the local core time of the transmitter, and obtain the phase difference of time source fusion or the phase difference when a single time source is valid, depending on the validity of the time source.

[0011] Based on the extracted frequency information, frequency source selection and frequency phase detection are performed to obtain the frequency difference between the local clock and the selected frequency source.

[0012] The phase of the local oscillator 1PPS signal at the transmitting end is adjusted according to the time fusion phase difference or when a single time source is valid, and the frequency of the local clock at the transmitting end is adjusted according to the frequency difference.

[0013] The various time-frequency signals, after phase and frequency adjustments, are re-encoded;

[0014] The re-encoded time source signal and frequency source signal are mixed into a single hybrid electrical signal using time-division multiplexing.

[0015] The hybrid electrical signal is converted into an optical signal and transmitted unidirectionally through a single optical fiber at a single wavelength;

[0016] The receiving end processing steps include:

[0017] The optical signal is received at a single wavelength through the single optical fiber and then converted back into a mixed electrical signal.

[0018] The mixed electrical signal is time-division multiplexed and decoded to separate and decode the time source signal and the frequency source signal;

[0019] Based on the time source information and phase obtained from decoding, the local core time of the transmitter is maintained, and the time source fusion phase difference or the phase difference when a single time source is valid is obtained based on the time source fusion algorithm according to the validity of the time source.

[0020] Based on the decoded frequency source signal, frequency phase detection is performed to obtain the frequency difference between the receiver's local clock and the frequency source.

[0021] The phase of the receiver's local oscillator 1PPS signal is adjusted according to the phase difference of the time source fusion at the receiver or the phase difference when a single time source is effective, and the frequency of the receiver's local clock is adjusted according to the frequency difference.

[0022] The adjusted time and frequency signals are encoded and output separately.

[0023] As a further solution, when both the time source 1PPS+TOD and the time source DCLS are valid, the time source fusion algorithm process includes:

[0024] Kalman filtering was performed on the phase difference data between time source 1PPS+TOD, time source DCLS and local oscillator 1PPS based on the time window.

[0025] Calculate the mean and variance of the phase difference data between the filtered time source 1PPS+TOD and the time source DCLS within the time window;

[0026] Based on the variance of the phase difference data between time source 1PPS+TOD and time source DCLS within the time window, the fusion weight of each time source is dynamically allocated, wherein the time source with the smaller variance is assigned a larger fusion weight.

[0027] The time fusion phase difference is calculated based on the fusion phase difference formula.

[0028] As a further solution, when only one time source is valid, no time source fusion algorithm is performed. Instead, the phase difference data of the valid time source is processed within a window of time, with the local core time as the reference. The data processing includes: first, performing Kalman filtering on the phase difference data of the valid time source, and then calculating the mean of the phase difference data of the valid time source relative to the local time based on the phase difference data after Kalman filtering.

[0029] When no time source is available, the local clock is used as the timer.

[0030] As a further solution, the frequency source is selected in descending order of priority: E1 signal, 1PPS+TOD signal, and DCLS signal; among them,

[0031] If no frequency source is available, the local clock will be used for hold.

[0032] If a valid frequency source exists, it is selected according to the frequency source selection rules, and the phase difference change data of the selected frequency source is processed within a time window using the local clock as a reference. The data processing includes: first, performing Kalman filtering on the phase difference change data; then, calculating the average value of the phase difference change of the frequency source relative to the local clock based on the Kalman filtered phase difference change data; and finally, calculating the frequency difference between the local clock and the frequency source based on the time interval between adjacent data.

[0033] On the other hand, the present invention provides a single-fiber unidirectional transmitter that employs a single-fiber unidirectional method for simultaneous transmission of multiple time-frequency signals as described in any of the preceding claims, including a 1PPS+TOD decoding and time phase extraction module, a DCLS decoding and time phase extraction module, an E1 decoding and frequency extraction module, a time and frequency phase detection module, a first local core time phase and clock frequency control module, a first 1PPS+TOD core time module, a first DCLS core time module, a first E1 parameter configuration module, a first 1PPS+TOD encoding module, a first DCLS encoding module, a first E1 encoding module, a time-frequency signal time-division multiplexing hybrid encoding control module, and an optical transmission module.

[0034] As a further solution, the first 1PPS+TOD core time module maintains the 1PPS+TOD core time according to the local core time of the transmitting end, the first DCLS core time module maintains the DCLS core time according to the local core time of the transmitting end, and the first E1 parameter configuration module completes the E1 parameter configuration according to the current frequency source status information.

[0035] As a further solution, the first 1PPS+TOD encoding module performs TOD encoding on the 1PPS+TOD signal; wherein, the 1PPS+TOD signal is aligned with the local oscillator 1PPS, the first 0.2S of 1S is used to transmit 1PPS, and the last 0.8S of 1S is used to transmit TOD.

[0036] The first DCLS encoding module encodes the DCLS signal; wherein the DCLS frame header is aligned with the local oscillator 1PPS.

[0037] In another aspect, the present invention also provides a receiver based on a single fiber unidirectional direction, employing a method for simultaneous transmission of multiple time-frequency signals based on a single fiber unidirectional direction as described in any of the preceding claims, including an optical receiving module, a time-division multiplexed hybrid time-frequency signal decoding and time phase-frequency extraction module, a second time and frequency phase detection module, a second local core time phase and clock frequency control module, a second 1PPS+TOD core time module, a second DCLS core time module, a second E1 parameter configuration module, a second 1PPS+TOD encoding module, a second DCLS encoding module, and a second E1 encoding module.

[0038] As a further solution, the second 1PPS+TOD core time module maintains the 1PPS+TOD core time according to the local core time of the receiver; the second DCLS core time module maintains the DCLS core time according to the local core time of the receiver; and the second E1 parameter configuration module completes the E1 parameter configuration according to the current frequency source status information.

[0039] As a further solution, the second 1PPS+TOD encoding module performs 1PPS+TOD encoding on the 1PPS+TOD signal, and the 1PPS+TOD signal is aligned with the local oscillator 1PPS of the receiving end.

[0040] The second DCLS encoding module encodes the DCLS signal, and the DCLS frame header is aligned with the local oscillator 1PPS at the receiving end;

[0041] The second E1 encoding module encodes the E1 signal and adjusts the phase of the E1 signal according to the local oscillator 1PPS to ensure that the local oscillator 1PPS is aligned with the E1 frame header.

[0042] Compared with related technologies, the present invention provides a method and system for simultaneous transmission of multiple time-frequency signals based on a single fiber and unidirectional transmission, which has the following advantages:

[0043] 1. This invention is based on a single-fiber, unidirectional, single-wavelength architecture, which has the advantages of simple hardware design, simple algorithm implementation, long transmission distance, low loss, low cost, strong anti-interference ability, high utilization of transmission medium, and convenient engineering deployment. The system is suitable for special scenarios with high security requirements, where only unidirectional time signal transmission is allowed, and the risk of data leakage is low.

[0044] 2. This invention uses time-division multiplexing technology to transmit multiple time-frequency signals simultaneously via a single-fiber, unidirectional, single-wavelength method. At the receiving end, all time-frequency signals are restored and output. Compared with wavelength division multiplexing schemes, this invention has simple hardware design, low algorithm implementation difficulty, low cost, and does not cause the problem of inconsistent transmission delay of time-frequency signals on different wavelengths.

[0045] 3. This invention proposes a time source fusion algorithm, which dynamically adjusts the weight of each time source phase difference in the fusion phase difference based on the variance of the local core time phase difference of different time sources, calculates the time source fusion phase difference, and finally adjusts the local oscillator 1PPS phase according to the fusion phase difference to improve the timing accuracy in the case of multiple time sources. Attached Figure Description

[0046] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0047] To more clearly illustrate the technical solutions in the embodiments of this application or related technologies, the accompanying drawings used in the description of the embodiments or related technologies will be briefly introduced below. Obviously, those skilled in the art can obtain other drawings based on these drawings without creative effort.

[0048] Figure 1 A schematic diagram illustrating the steps of a method for simultaneous transmission of multiple time-frequency signals based on a single fiber and unidirectional direction, provided by the present invention;

[0049] Figure 2 This is a schematic diagram of the transmitting end structure provided by the present invention;

[0050] Figure 3 This is a schematic diagram of the receiver structure provided by the present invention;

[0051] Figure 4 A schematic diagram of a multi-time-frequency signal simultaneous transmission system based on a single fiber and unidirectional direction is provided for this invention.

[0052] Figure 5 This is a schematic diagram of the transmission of 1PPS+TOD between the transmitting and receiving ends provided by the present invention;

[0053] Figure 6 This invention provides schematic diagrams of various time-division multiplexing transmissions of time-frequency signals.

[0054] The purpose, features, and advantages of this application will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0055] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0056] Please see Figure 1 This embodiment proposes a method for simultaneous transmission of multiple time-frequency signals based on a single-fiber unidirectional transmission, including a transmitting end processing step and a receiving end processing step; wherein,

[0057] The various time-frequency signals include time source signals and frequency source signals; the time source signals include 1PPS+TOD signals and DCLS signals, and the frequency source signals include 1PPS+TOD signals, DCLS signals, and E1 signals;

[0058] The sending end processing steps include:

[0059] It receives time source signals and frequency source signals, decodes the time source signals to obtain time source information and phase, and decodes and extracts the frequency source signals to obtain frequency information.

[0060] Based on the time source information and phase obtained from decoding, maintain the local core time of the transmitter, and obtain the phase difference of time source fusion or the phase difference when a single time source is valid, depending on the validity of the time source.

[0061] Based on the extracted frequency information, frequency source selection and frequency phase detection are performed to obtain the frequency difference between the local clock and the selected frequency source.

[0062] The phase of the local oscillator 1PPS signal at the transmitting end is adjusted according to the time fusion phase difference or when a single time source is valid, and the frequency of the local clock at the transmitting end is adjusted according to the frequency difference.

[0063] The various time-frequency signals, after phase and frequency adjustments, are re-encoded;

[0064] The re-encoded time source signal and frequency source signal are mixed into a single hybrid electrical signal using time-division multiplexing.

[0065] The hybrid electrical signal is converted into an optical signal and transmitted unidirectionally through a single optical fiber at a single wavelength;

[0066] The receiving end processing steps include:

[0067] The optical signal is received at a single wavelength through the single optical fiber and then converted back into a mixed electrical signal.

[0068] The mixed electrical signal is time-division multiplexed and decoded to separate and decode the time source signal and the frequency source signal;

[0069] Based on the time source information and phase obtained from decoding, the local core time of the transmitter is maintained, and the time source fusion phase difference or the phase difference when a single time source is valid is obtained based on the time source fusion algorithm according to the validity of the time source.

[0070] Based on the decoded frequency source signal, frequency phase detection is performed to obtain the frequency difference between the receiver's local clock and the frequency source.

[0071] The phase of the receiver's local oscillator 1PPS signal is adjusted according to the phase difference of the time source fusion at the receiver or the phase difference when a single time source is effective, and the frequency of the receiver's local clock is adjusted according to the frequency difference.

[0072] The adjusted time and frequency signals are encoded and output separately.

[0073] Based on this, this embodiment also provides, for example... Figure 4The system shown is a multi-time and frequency signal simultaneous transmission system based on single-fiber unidirectional transmission. The system is based on multiple time and frequency signal inputs, and uses single-fiber unidirectional single-wavelength time division multiplexing transmission for time synchronization to complete the output of multiple time and frequency signals at the receiving end.

[0074] The system can be divided into two parts: a transmitter and a receiver.

[0075] like Figure 2 As shown, the sending end mainly includes the following functional modules:

[0076] The system includes a 1PPS+TOD decoding and time phase extraction module, a DCLS decoding and time phase extraction module, an E1 decoding and frequency extraction module, a time and frequency phase detection module, a first local core time phase and clock frequency control module, a first 1PPS+TOD core time module, a first DCLS core time module, a first E1 parameter configuration module, a first 1PPS+TOD encoding module, a first DCLS encoding module, a first E1 encoding module, a time-frequency signal time-division multiplexing hybrid encoding control module, and an optical transmission module.

[0077] like Figure 3 As shown, the receiving end mainly includes the following functional modules:

[0078] The system includes an optical receiving module, a time-division multiplexed hybrid time-frequency signal decoding and time phase-frequency extraction module, a second time and frequency phase detection module, a second local core time phase and clock frequency control module, a second 1PPS+TOD core time module, a second DCLS core time module, a second E1 parameter configuration module, a second 1PPS+TOD encoding module, a second DCLS encoding module, and a second E1 encoding module.

[0079] The system proposed in this invention can receive 1PPS+TOD, DCLS and E1 signal inputs.

[0080] The time sources are 1PPS+TOD and DCLS, and the frequency sources are E1, 1PPS+TOD, and DCLS.

[0081] When time sources 1PPS+TOD and DCLS are both valid, the two time sources are fused according to the time source fusion algorithm. Using the local core time as a reference, the phase difference between the two time sources is processed separately within a time window. First, Kalman filtering is applied to the data. Based on the Kalman filtered data, the mean and variance of the phase difference between each time source relative to the local core time are calculated. Then, based on the variance ratio of the phase differences between the two time sources, the fusion phase difference weight of the phase difference between the two time sources is determined. The smaller the relative variance of the time source phase difference, the greater the fusion weight. Finally, after calculating the fusion phase difference of the time sources, the local core time is phase-adjusted. After the phase adjustment is completed, the sample window is cleared and the counting is restarted.

[0082] When only one time source is valid, no fusion processing is performed. Instead, the local core time is used as the reference to process the phase difference of the time source within a time window. First, Kalman filtering is applied to the data. Then, the average phase difference between the time source and the local time is calculated based on the Kalman filtered data. Finally, the local core time is phase-adjusted based on the average value. After the phase adjustment is completed, the sample window is cleared and the counting is restarted. When no time source is valid, the system uses the local clock as the hold.

[0083] Frequency sources are selected in descending order of priority: E1, 1PPS+TOD, and DCLS, with E1 having the highest priority.

[0084] If no frequency source is available, the system uses the local clock as the hold. If a frequency source is available, it selects one according to the frequency source selection rules and processes the phase difference change of the selected frequency source (the phase difference at the current moment minus the phase difference at the previous measurement moment) within a window of time, using the local clock as the reference. First, the data is Kalman filtered, and the mean value of the phase difference change of the frequency source relative to the local clock is calculated based on the Kalman filtered data. Then, the frequency difference between the local clock and the frequency source is calculated based on the time interval between two adjacent data points. Finally, the local clock is frequency-adjusted based on the frequency difference and phase difference. After the frequency adjustment is completed, the sample window is cleared and the counting starts again.

[0085] The time source fusion algorithm proposed in this system has the following process:

[0086] Based on the time window n, the phase difference data between the time source 1PPS+TOD and the time source DCLS and the local oscillator are respectively subjected to Kalman filtering. The phase difference data between the time source and the local oscillator after Kalman filtering can be expressed as: and , This represents the i-th data point within the time window after the phase difference data between the time source 1PPS+TOD and the local oscillator has been processed by Kalman filtering. This represents the i-th data point within the time window after the phase difference data between the DCLS time source and the local oscillator has been processed by Kalman filtering. .

[0087] The average value of the phase difference data between the time source 1PPS+TOD and the local oscillator after Kalman filtering is based on this time window. The calculation formula is Its variance The calculation formula is The mean value of the phase difference data between the DCLS time source and the local oscillator after Kalman filtering, based on this time window. The calculation formula is Its variance The calculation formula is .

[0088] The weight of the fused phase difference between the time source 1PPS+TOD and the local oscillator phase difference The calculation formula is: The weight of the fused phase difference between the time source DCLS and the local oscillator phase difference. The calculation formula is: .

[0089] Time fusion phase difference The calculation formula is expressed as: .

[0090] The 1PPS+TOD decoding and time phase extraction module supports the decoding of 1PPS+TOD signals according to the YD / T 2375-2019 standard. The decoded time information is used to maintain the local core time and to provide the 1PPS signal to the time and frequency phase detection modules.

[0091] The DCLS decoding and time phase extraction module supports DCLS signal decoding according to the GJB 2991A-2008 standard. The decoded time information is used to maintain the local core time, and the 1PPS signal extracted from the DCLS signal is provided to the time and frequency phase detection module. The 1PPS signal is restored based on the DCLS frame header.

[0092] The E1 decoding and clock extraction module supports E1 signal decoding according to the ITU-T G.704 standard and can extract a 2.048MHz clock from the E1 signal, which is provided to the time and frequency phase detection modules.

[0093] The first-time and frequency phase detection module (transmitter) supports time source fusion processing, frequency source selection, time phase detection, and frequency phase detection. The module can receive the recovered 1PPS signal from the 1PPS+TOD and DCLS signals, and the recovered 2.048MHz clock from the E1 signal. The time sources are 1PPS+TOD and DCLS, and the frequency sources are E1, 1PPS+TOD, and DCLS. Time phase detection measures the phase difference between the local oscillator 1PPS and the time source, while frequency phase detection measures the phase difference between the local clock and the frequency source.

[0094] When time sources 1PPS+TOD and DCLS are both valid, the two time sources are fused according to the time source fusion algorithm. Using the local core time as the reference, the phase difference between the two time sources is processed separately within a time window. First, Kalman filtering is applied to the data. Based on the Kalman filtered data, the mean and variance of the phase difference between each time source relative to the local core time are calculated. Then, based on the variance ratio of the phase differences between the two time sources, the fusion phase difference weight of the two time source phase differences is determined. The smaller the relative variance of the time source phase difference, the greater the fusion weight. Finally, the fusion phase difference of the time sources is calculated.

[0095] When only one time source is valid, no fusion processing is performed. The local core time is used as the reference to process the phase difference of the time source within a window of time. First, Kalman filtering is performed on the data, and then the average value of the phase difference of the time source relative to the local time is calculated based on the Kalman filtered data. When no time source is valid, the system uses the local clock as the hold.

[0096] Frequency sources are selected in descending order of priority: E1, 1PPS+TOD, and DCLS, with E1 having the highest priority. If no frequency source is available, the system uses the local clock as the hold. If a frequency source is available, it is selected according to the frequency source selection rules. The system then processes the phase difference change of the selected frequency source (the phase difference at the current moment minus the phase difference at the previous measurement moment) within a time window, using the local clock as a reference. First, the data is Kalman filtered. The mean value of the phase difference change of the frequency source relative to the local clock is calculated based on the Kalman filtered data. Then, the frequency difference between the local clock and the frequency source is calculated based on the time interval between two adjacent data points.

[0097] The first local core time phase and clock frequency control module (transmitter) completes core time phase control and clock frequency control. The module maintains the transmitter's local core time based on the time information obtained from the time source decoding, and controls the phase of the transmitter's local oscillator (1PPS) based on the fused phase difference or phase difference provided by the time and frequency phase detection modules. The module controls the transmitter's local clock frequency based on the frequency difference and phase difference between the transmitter's local clock and the frequency source provided by the time and frequency phase detection modules.

[0098] The first 1PPS+TOD core time module (sender) maintains the 1PPS+TOD core time based on the sender's local core time.

[0099] The first DCLS core time module (sender) maintains the DCLS core time based on the sender's local core time.

[0100] The first E1 parameter configuration module (transmitter) completes the E1 parameter configuration based on the current frequency source status information.

[0101] The first 1PPS+TOD encoding module (transmitter) performs TOD encoding according to the YD / T 2375-2019 standard. The 1PPS+TOD signal is aligned with the local oscillator 1PPS. The first 0.2 seconds of the 1S signal are used to transmit 1PPS, and the last 0.8 seconds of the 1S signal are used to transmit TOD. See the schematic diagram of 1PPS+TOD transmission. Figure 5 ;

[0102] The first DCLS encoding module (transmitter) encodes according to the GJB 2991A-2008 standard, and the DCLS frame header is aligned with the local oscillator 1PPS.

[0103] The first E1 encoding module (transmitter) encodes according to the ITU-T G.704 standard and adjusts the phase of the E1 signal according to the local oscillator 1PPS to ensure that the local oscillator 1PPS is aligned with the E1 frame header.

[0104] The time-division multiplexing hybrid coding control module for time-frequency signals mixes and encodes 1PPS+TOD, DCLS, and E1 signals using time-division multiplexing. Each time-frequency signal has a 1-second time slot for time-division multiplexing, with a 3-second cycle. The 1PPS+TOD, DCLS, and E1 signals are transmitted cyclically. A schematic diagram of time-division multiplexing transmission of multiple time-frequency signals is shown below. Figure 6 As shown.

[0105] The optical transmission module converts electrical signals into optical signals and transmits the optical signals through optical fibers.

[0106] The optical receiver module receives the optical signal and converts it into an electrical signal.

[0107] The time-division multiplexing hybrid time-frequency signal decoding and time phase-frequency extraction module identifies the 1PPS+TOD, DCLS, and E1 signals from the hybrid time-frequency signal based on the characteristics of the 1PPS+TOD, DCLS, and E1 signals. It then decodes the 1PPS+TOD, DCLS, and E1 signals and obtains time and frequency status information for local core time maintenance and receiver E1 parameter configuration. Simultaneously, it recovers and extracts the respective PPS signals from the 1PPS+TOD and DCLS signals for use by the receiver's time and frequency phase detection modules. It also extracts a 2.048MHz clock from the E1 signal and provides it to the clock and frequency phase detection modules.

[0108] The second time and frequency phase detection module (receiver) supports time source fusion processing, time phase detection, and frequency phase detection. The module receives 1PPS+TOD and the PPS extracted from DCLS as the time source, and receives the 2.048MHz clock recovered from the E1 signal as the frequency source.

[0109] The time phase detector completes the phase difference measurement between the local oscillator 1PPS and the time source, while the frequency phase detector completes the phase difference measurement between the local clock and the frequency source.

[0110] During time phase detection, the two time sources are fused using a time source fusion algorithm. Using 1PPS of local oscillator as a reference, the phase difference between the two time sources is processed within a window of time. First, Kalman filtering is applied to the data. Based on the Kalman filtered data, the mean and variance of the phase difference between each time source relative to the local time are calculated. Then, based on the variance ratio of the phase differences between the two time sources, the weight of the fused phase difference is determined. The smaller the relative variance of the time source, the greater the fusion weight of the phase difference. Finally, the fused phase difference of the time sources is calculated.

[0111] When performing frequency phase detection, the local clock is used as a reference to process the phase difference change of the frequency source (the phase difference at the current moment minus the phase difference at the previous measurement moment) within a window time. First, Kalman filtering is performed on the data. The average value of the phase difference change of the frequency source relative to the local clock is calculated based on the Kalman filtered data. Then, the frequency difference between the local clock and the frequency source is calculated based on the time interval between two adjacent data.

[0112] The second local core time phase and clock frequency control module (receiver) completes core time phase control and clock frequency control. The module maintains the local core time based on the time information decoded from the receiver's time source, and controls the phase of the receiver's local oscillator (1PPS) based on the fused phase difference provided by the receiver's time and frequency phase detection modules. The module controls the receiver's local clock frequency based on the frequency difference and phase difference between the local clock and the frequency source provided by the time and frequency phase detection modules. The second 1PPS+TOD core time module (receiver) maintains the 1PPS+TOD core time based on the receiver's local core time.

[0113] The second DCLS core time module (receiver) maintains the DCLS core time based on the receiver's local core time.

[0114] The second E1 parameter configuration module (receiver) completes the E1 parameter configuration based on the current frequency source status information.

[0115] The second 1PPS+TOD encoding module (receiver) performs 1PPS+TOD encoding according to the YD / T 2375-2019 standard, and the 1PPS+TOD signal is aligned with the local oscillator 1PPS of the receiver.

[0116] The second DCLS encoding module (receiver) encodes according to the GJB 2991A-2008 standard, and the DCLS frame header is aligned with the receiver's local oscillator 1PPS.

[0117] The second E1 encoding module (receiver) encodes according to the ITU-T G.704 standard.

[0118] In summary, the simultaneous transmission system for multiple time-frequency signals based on a single fiber and unidirectional direction proposed in this invention has the following corresponding transmission method flow:

[0119] Step S1: Input time and frequency signals;

[0120] Step S2: Decoding the time-frequency signal and extracting the time-phase-frequency;

[0121] Step S3: Transmitter time phase detection, time source fusion, frequency source selection, and frequency phase detection;

[0122] Step S4: Control of local core time, local oscillator 1PPS phase, and clock frequency at the transmitting end;

[0123] Step S5: Transmitter 1PPS+TOD, DCLS core time maintenance, E1 parameter configuration;

[0124] Step S6: Transmitter uses 1PPS+TOD, DCLS, and E1 encoding;

[0125] Step S7: Time-division multiplexing hybrid control coding of time-frequency signals;

[0126] Step S8: Electro-optical conversion;

[0127] Step S9: Single-fiber unidirectional same-wavelength transmission;

[0128] Step S10: Photoelectric conversion;

[0129] Step S11: Decoding and extracting time phase and frequency of time-division multiplexed hybrid time-frequency signal;

[0130] Step S12: Receiver-side time phase detection, time source fusion, and frequency phase detection;

[0131] Step S13: Control of local core time, local oscillator 1PPS phase and clock frequency at the receiver;

[0132] Step S14: Receiver 1PPS+TOD, DCLS core time maintenance, E1 parameter configuration;

[0133] Step S15: Receiver performs 1PPS+TOD, DCLS, and E1 encoding;

[0134] Step S16: Output time and frequency signals.

[0135] The above are only some embodiments of this application and do not limit the patent scope of this application. All equivalent structural transformations made under the technical concept of this application and using the contents of the specification and drawings of this application, or direct / indirect applications in other related technical fields, are included in the patent protection scope of this application.

Claims

1. A single-fiber unidirectional-based multi-time-frequency signal simultaneous transmission method, characterized in that, The method comprises a sending end processing step and a receiving end processing step. The multiple time-frequency signals comprise time source signals and frequency source signals; the time source signals comprise 1PPS+TOD signals and DCLS signals, and the frequency source signals comprise 1PPS+TOD signals, DCLS signals and E1 signals; The sending end processing step comprises: receiving the time source signals and the frequency source signals, decoding the time source signals to obtain time source information and a phase, and decoding and frequency extracting the frequency source signals to obtain frequency information; based on the decoded time source information and the phase, maintaining a local core time of the sending end, and according to the validity of the time sources, obtaining a time source fusion phase difference or a phase difference when a single time source is valid; based on the extracted frequency information, performing frequency source selection and frequency phase discrimination to obtain a frequency difference between a local clock and the selected frequency source; adjusting the phase of a local 1PPS signal of the sending end according to the time source fusion phase difference or the phase difference when a single time source is valid, and adjusting the frequency of the local clock of the sending end according to the frequency difference; re-encoding the time-frequency signals after the phase and frequency adjustment; mixing the re-encoded time source signals and the frequency source signals into a mixed electrical signal through time division multiplexing; converting the mixed electrical signal into an optical signal, and transmitting the optical signal in a single wavelength through a single optical fiber in a single direction; the receiving end processing step comprises: receiving the optical signal in a single wavelength through the single optical fiber, and converting the optical signal back into the mixed electrical signal; performing time division multiplexing decoding on the mixed electrical signal to separate and decode the time source signals and the frequency source signals; based on the decoded time source information and the phase, maintaining the local core time of the sending end, and according to the validity of the time sources, obtaining a time source fusion phase difference or a phase difference when a single time source is valid based on a time source fusion algorithm; based on the decoded frequency source signals, performing frequency phase discrimination to obtain a frequency difference between a local clock of the receiving end and the frequency source; adjusting the phase of a local 1PPS signal of the receiving end according to the time source fusion phase difference or the phase difference when a single time source is valid, and adjusting the frequency of the local clock of the receiving end according to the frequency difference; encoding and outputting the time-frequency signals after the adjustment; when the time source 1PPS+TOD and the time source DCLS are both valid, the time source fusion algorithm process comprises: performing Kalman filtering on the phase difference data of the time source 1PPS+TOD, the time source DCLS and the local 1PPS based on a time window; calculating the mean and variance of the filtered phase difference data of the time source 1PPS+TOD and the time source DCLS within the time window; dynamically allocating fusion weights of the time sources according to the variances of the time source 1PPS+TOD and the time source DCLS within the time window, wherein the time source with a smaller variance is allocated a larger fusion weight; calculating the time source fusion phase difference according to a fusion phase difference formula.

2. The single-fiber unidirectional-based multi-time-frequency signal simultaneous transmission method according to claim 1, characterized in that, When only one time source is valid, no time source fusion algorithm is processed, and the phase difference data of the valid time source is processed in a window time based on the local core time; wherein, the data processing includes: first, the phase difference data of the valid time source is subjected to Kalman filtering, and then the mean value of the phase difference data of the valid time source relative to the local time is calculated according to the Kalman filtered phase difference data; When no time source is valid, the local clock is kept.

3. The single fiber unidirectional based multi-time-frequency signal simultaneous transmission method according to claim 1, characterized in that, The frequency source is selected according to the priority order of E1 signal, 1PPS+TOD signal and DCLS signal from high to low; wherein, If no frequency source is valid, the local clock is kept; If there is a valid frequency source, the frequency source is selected according to the frequency source selection rule, and the phase difference change data of the selected frequency source is processed in a time window based on the local clock; wherein, the data processing includes: first, the phase difference change data is subjected to Kalman filtering, and then the mean value of the phase difference change of the frequency source relative to the local clock is calculated according to the Kalman filtered phase difference change data, and then the frequency difference between the local clock and the frequency source is calculated according to the time interval between adjacent data.

4. A single-fiber one-way transmitting end using the same-time frequency signal simultaneous transmission method of any one of claims 1 to 3. The first 1PPS+TOD core time module maintains the 1PPS+TOD core time according to the local core time of the sending end, the first DCLS core time module maintains the DCLS core time according to the local core time of the sending end, and the first E1 parameter configuration module completes the E1 parameter configuration according to the current frequency source state information.

5. A single fiber one-way based transmitting end according to claim 4, characterized in that, The first 1PPS+TOD encoding module encodes the 1PPS+TOD signal; wherein, the 1PPS+TOD signal is aligned with the local 1PPS, the first 0.2S of 1S is used for transmitting 1PPS, and the last 0.8S of 1S is used for transmitting TOD; 6. A single fiber one-way based transmitting end according to claim 4, characterized in that, The first DCLS encoding module encodes the DCLS signal; wherein, the DCLS frame header is aligned with the local 1PPS. The first 1PPS+TOD core time module maintains the 1PPS+TOD core time according to the local core time of the sending end, the first DCLS core time module maintains the DCLS core time according to the local core time of the sending end, and the first E1 parameter configuration module completes the E1 parameter configuration according to the current frequency source state information.

7. A single-fiber one-way based receiving end using the single-fiber one-way based multi-time-frequency signal simultaneous transmission method according to any one of claims 1 to 3. The first 1PPS+TOD encoding module encodes the 1PPS+TOD signal; wherein, the 1PPS+TOD signal is aligned with the local 1PPS, the first 0.2S of 1S is used for transmitting 1PPS, and the last 0.8S of 1S is used for transmitting TOD; The first DCLS encoding module encodes the DCLS signal; wherein, the DCLS frame header is aligned with the local 1PPS. The first 1PPS+TOD core time module maintains the 1PPS+TOD core time according to the local core time of the sending end, the first DCLS core time module maintains the DCLS core time according to the local core time of the sending end, and the first E1 parameter configuration module completes the E1 parameter configuration according to the current frequency source state information.

8. The single-fiber one-way based receiving end according to claim 7, characterized in that, The second 1PPS+TOD core time module maintains 1PPS+TOD core time according to the local core time of the receiving end; the second DCLS core time module maintains DCLS core time according to the local core time of the receiving end; and the second E1 parameter configuration module completes E1 parameter configuration according to current frequency source state information.

9. The single-fiber one-way based receiving end according to claim 7, characterized in that, The second 1PPS+TOD encoding module encodes 1PPS+TOD signals, and the 1PPS+TOD signals are aligned with the receiving end local 1PPS; The second DCLS encoding module encodes DCLS signals, and the DCLS frame header is aligned with the receiving end local 1PPS; The second E1 encoding module encodes E1 signals, adjusts the E1 signal phase according to the local 1PPS, and ensures that the local 1PPS is aligned with the E1 frame header.

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